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I really liked this one, although I think I probably liked Fast 5 slightly more. But it just made me relive all them Han feels.
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As for all the DIESEL FUEL haters, I think you have to accept going into this movie that it's not trying to be a piece of cinematic art like The Godfather, but that doesn't really detract from the movies being entertaining in the same way action flicks are. Are some of the stunts unrealistic and/or physically impossible (the whole vault chase in Fast Five), sure, but it's the racing equivalent of action hero bullet evasion with Chuck Norris and Sly never getting hit as they destroy entire armies. Think "The Expendables" with cars.
And the main movies of the franchise (1-4-5-6) do get better as they progress. Basically
1 - Basic character introductions with some 10 second racing, a decent amount of street racing,
2 - Served to introduce Tyrese and Ludacris into the franchise, but was otherwise a money-grab sequel that failed because they couldn't bring DIESEL FUEL back and had to center the movie around Paul Walker
3 - Again they failed to get DIESEL FUEL back, and given how poorly Walker did on his own, they tried to transition to a new locale and a new set of characters. The protagonist and his entourage didn't really appeal to me, but Sung Kang's Han made this worth watching imo. (This is when Justin Lin took over the franchise as director)
4 - Diesel finally returns to the series so this movie is primarily about him dealing with Letty's death, and Brian's decision between his life as a cop and what he sees in Dom's family.
5 - Brings the periphery characters from 2/3/4 back in to join DIESEL FUEL and Paul Walker and establish the core of the new heist crew. They start by facing off against THE ROCK.
6 - Working with THE ROCK this time as a counter-heist crew. (Justin Lin leaves as director. Also, F&F3: Tokyo Drift takes place right after this movie chronologically)
7 - PROBABLY MORE COUNTER-HEIST... BUT THIS TIME IT'S PERSONAL
You should watch them at some point when they play for free on cable to get the story and background, because it will make the character side stories a lot more meaningful, but from 5 and on, the movies are very different.
I read a long time ago that this was a purposeful direction change to get a bigger audience -- the audience for a street racing movie is semi-limited because it has thug overtones and such. But a heist movie appeals to a broader demographic because it allows them to emphasize the honorable aspect of the criminals with their family honor when they are set opposite less honorable criminals (druglords in 4/5, then practically terrorists in 6). This also plays into why the crew ended up working with The Rock instead of being flat out criminals.